In image recognition, a feature of an image is evaluated so as to determine whether an area in the image is a specific object such as a human, for example. Various feature descriptors are known that are used for evaluating features of images.
As one of the various feature descriptors, a histogram-based feature descriptor such as histograms of oriented gradients (HOG) feature descriptor is known. In the use of the histogram-based feature descriptor, a total value of the feature descriptors of respective pixels in an area is used for evaluation. When an area in an image is evaluated using such a histogram-based feature descriptor, a calculation of the feature descriptors of respective pixels and a calculation for accumulating the feature descriptors in the area are performed, and furthermore, a calculation should be performed for evaluating the accumulated feature descriptors. As a result, a high calculation cost is required.